. Electric railway journal . s and overhead wires, lightning conditions arenot very severe, but the number of cars to be protectedis very large. In such cases a comparatively cheap results for the protection of station apparatus, especiallywhere two are used in parallel. The WestinghouseMP or multipath type of railway arrester consistsof a molded carborundum block in series with a smallspark gap, all inclosed in a weatherproof galvanizediron box. The carborundum block has very high re-sistance up to a certain critical voltage above whichit breaks down into a multitude of series and parallelspa
. Electric railway journal . s and overhead wires, lightning conditions arenot very severe, but the number of cars to be protectedis very large. In such cases a comparatively cheap results for the protection of station apparatus, especiallywhere two are used in parallel. The WestinghouseMP or multipath type of railway arrester consistsof a molded carborundum block in series with a smallspark gap, all inclosed in a weatherproof galvanizediron box. The carborundum block has very high re-sistance up to a certain critical voltage above whichit breaks down into a multitude of series and parallelspark gaps having little or no resistance. After thehigh voltage passes, the discharge is quenched by thesubdivision of the current into many minute series andparallel arcs, which individually have insufficient volt-age to maintain themselves. The cooling effect of thegreat mass of the block, in intimate contact with thearcs, also aids greatly in stopping the flow of the discharge has been stopped the block regains. Trolley Wire Trolley Base10-Ampere Fuse (when used)Lightning ArresterGrounded on nearest steel \ Grounded to steel Lightningcar frame Arrester -Trolley Connect ground lead tobody bosfer and truck frame cture of all steel car ,„, , . k ^-^\r~^ | Whe?hCj\ a Gf> Wheel (J 7[Q- Wheel B = Ground wire (use no metalconduit) used on cars that arenot all steel Ground on truck frame Motor1-2 Rail- Motor3-4 Motor ground lead ETG. 1—DIAGRAM OP CONNECTIONSFOR MOUNTING ARRESTERON CAR ROOF FIG. 2—METHOD OF MOUNT-ING AND GROUNDINGARRESTER ON ALL-STEEL CAR BODY c Car Roof , \ Circuit7I Breaker Controller [Conduit may.[beusedhere\[as shown by \[dotted lines \ (when used). To Motors etc Trolley- Trolley Base CarBody—->Ji I i 10-Ampere Fuse(when used) Metal Conduit shouldnot be used here ghtnina Arrester Ground on Truck Frame FIG. 3—DIAGRAM OF CONNECTIONSFOR MOUNTING ARRESTERUNDERNEATH CAR type of arrester could be used. On interurban lines,especially those loc
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